Populations of fish species desirable for human consumption are continuing to decline. However, soft tissue textured fish, such as Arrowtooth Flounder, Pacific Dover Sole, Pacific Sand Dab, Pacific Mackerel, Pacific Whiting or Hake, English Sole, Argentine Whiting, Chilean Whiting, Atlantic Whiting, Peruvian Whiting, and some species of Salmon, are highly abundant, but possess few viable commercial applications. The background is presented herein only by way of example to whiting. Whiting is vastly abundant worldwide, has few commercial uses except for Surimi, must be handled carefully due to its soft texture, and is susceptible to protease tissue disintegration.
Whiting and other fish are commercially undervalued and underused because the texture of their tissue is inherently soft, their tissue becomes soft before it can be processed and consumed, or the tissue tends undesirably to flake apart into small pieces. Fish tissue exhibiting softness is typically so weak that it disintegrates easily, even when the fish are handled delicately and cooked immediately by conventional methods.
Conventional cooking methods, including steaming, microwaving, frying, boiling, and baking, do not achieve significant tissue texture improvement even though certain conventional cooking procedures may inactivate some protease and other enzymes thought to cause softening. For example, the moisture-intensive cooking procedures tend to cause tissue disintegration while conventional dry heat cooking methods, such as grilling and baking, transfer the heat too slowly to inactivate enzymes and prevent internal tissue softening.
Several materials, such as egg white, potato starch, and beef plasma protein, are known to inhibit tissue-softening protease enzymes. The effectiveness of these treatments for controlling fish tissue softening is, however, limited because the protease and other enzymes are present throughout the fish tissue. Standard immersion and other surface treatment procedures do not effectively penetrate the deeper tissues, so internal tissue softening continues. Even if a protease inhibitor could be distributed throughout the fish tissue, some softening would still occur during conventional cooking procedures. For example, protease inhibitors may not affect all biochemical factors that contribute to softening. Furthermore, enzyme inhibition will not restore the original tissue texture to tissue that has already softened, i.e., the softening is irreversible. Some fish species inherently have weakly bound tissue that disintegrates regardless of the inactivation of protease enzymes.
U.S. Pat. No. 4,407,831 of Swartz describes a method for nutritionally fortifying fish tissue with protein by injection with water soluble soy, milk, and particularly whey protein derivatives. The patent also describes a phosphate pretreatment to minimize drip losses. The patent does not disclose or suggest tissue firming methods.